This invention relates to oils and fats resistant to autoxidation, and particularly to a method of improving the oxidation resistance of an animal or vegetal fat or oil.
Animal and vegetal fat and oils are triglycerides of carboxylic aliphatic acids. When exposed to atmospheric oxygen, particularly at elevated temperature, they are subject to oxidation (autoxidation) which impairs their taste, and may make them unfit for human consumption. Autoxidation of fats and oils is catalyzed by heavy metals, such as iron, copper, and nickel, even in trace amounts which may be picked up from processing equipment as during hydrogenation or refining. The conventional methods for separating the hydrogenation catalysts from processed fats or oils cannot remove the last traces of catalyst metal which are sufficient to promote autoxidation.
Attempts have been made to render the traces of heavy metals inactive by mixing chelating agents with the fats and oils, but the heavy metal complexes formed thereby are decomposed at the elevated temperatures used normally in frying and like common applications of edible fats and oils, and cannot stabilize frying fat or oil for extended periods and repeated use.